A light emitting diode driving semiconductor circuit for driving a light emitting diode (LED) and a light emitting diode driving apparatus including the same are recently developed and put into practical use. Conventional light emitting diode driving apparatus (illuminating apparatus) is disclosed in JP-A-2000-30877 (patent document 1). The conventional light emitting diode driving apparatus will be described with reference to FIG. 19.
The conventional light emitting diode driving circuit in FIG. 19 includes an alternating-current power supply AC, a full-wave rectifier circuit DB connected to the alternating-current power supply AC, LED arrays 1, . . . , m (m is an integer greater than or equal to two) of a plurality of lines formed by connecting in series a plurality of LEDs, current-limiting elements Z1, . . . , Zm such as resistors each having one end connected to a cathode side of each LED array 1, . . . , m and other end connected in common to a negative output terminal of the full-wave rectifier circuit DB, and a switching means SW selectively switching to connect an anode side of each LED array 1, . . . , m to either a positive output terminal of the full-wave rectifier circuit DB or one end of the alternating-current power supply AC.
The conventional light emitting diode driving apparatus selects either half-wave conduction by the alternating-current power supply or full-wave conduction by the full-wave rectifier circuit by means of the switching means SW with respect to each LED array of a plurality of lines. A current value flowing in each LED array 1, . . . , m is thereby determined. For example, the illuminating apparatus of m=2 has a dimming function of four steps.
Patent document 1: JP-A-2000-30877